Cellulose nanofiber (CNF) has attracted significant attention as a next-generation insulating material due to its ecofriendly nature and outstanding functionalities. However, conventional kraft insulation paper suffers from limited dielectric breakdown strength and long-term reliability under high-voltage conditions, highlighting the need for alternative materials. In this study, kraft pulp was combined with five types of CNFs (A, B, C: wood-based / D, E: non-wood-based) to fabricate composite insulation papers, and their electrical and mechanical properties were systematically evaluated. The results showed that CNF incorporation generally enhanced density and tensile strength, while certain types contributed to lowering dielectric constant and improving breakdown strength. Among the wood-based CNFs, type C exhibited the most balanced performance in terms of dielectric stability and mechanical reinforcement. Among the non-wood-based CNFs, type E demonstrated notable improvements in structural compactness and tensile strength, suggesting favorable reliability. Therefore, this study identifies CNF C among wood-based types and CNF E among non-wood-based types as the most promising candidates for insulation performance enhancement, suggesting their applicability as next-generation insulating materials for power equipment and ecofriendly electronic devices.

Mullite (3Al₂O₃·2SiO₂) has emerged as a promising candidate for high-temperature structural materials due to its erosion resistance, chemical and thermal stabilities, relatively low thermal expansion coefficient, excellent thermal shock and creep resistances, and low dielectric constant. However, since the pure mullite sintering temperature is as high as 1,600~1,700℃, there is an increasing need for a sintering additive capable of improving the strength characteristics while lowering the sintering temperature. Herein we have tried to obtain the optimal sintering additive composition by adding MgO, Cr₂O₃, and Y₂O₃ to mullite, followed by sintering at 1,325~1,550℃ for 2 h. With additives of 2 wt% of MgO, 2 wt% of Cr₂O₃, 4 wt% of Y₂O₃, A density of 3.23 g/cm³ was obtained for the sintered body at 1,350℃ upon using 2 wt% MgO, 2 wt% Cr₂O₃, and 4 wt% Y₂O₃ as additives. The three-point flexural strength of that was 275 MPa and the coefficient of thermal expansion (CTE) was 4.15 ppm/℃.

3YSZ + (x) Al₂O₃ composites (x = 20, 40, 60, 80 wt%) were fabricated and the influences of particle sizes of Al₂O₃ on their microstructures and mechanical properties were investigated with XRD, SEM, vickers hardness and fracture toughness. Al₂O₃-3YSZ composites containing Al₂O₃ powder of a 0.3 μm and an 1.0 μm, which are here in after named as Al2O3(0.3 μm)-3YSZ and Al₂O₃ (1.0 μm)-3YSZ, respectively, were made by mixing raw materials, uni-axial pressing and sintering at 1,400℃, 1,500℃, and 1,600℃. Al₂O₃ (0.3 μm)-3YSZ composites show the higher density and the better mechanical properties than Al₂O₃ (1.0 μm)-3YSZ composites. The Vickers hardness of the Al₂O₃ (0.3 μm)-3YSZ composites show a peak value of 1,997 Hv at the content of 60 wt% Al₂O₃, which is a slightly higher value in comparison with 1,938 Hv of the Al2O3(1.0 μm)-3YSZ composite. However, the fracture toughness of Al₂O₃-3YSZ composites monotonically increases with decreasing the content of Al₂O₃ without any peak values. Al₂O₃ (0.3 μm)-3YSZ and Al₂O₃ (1.0 μm)-3YSZ composites sintered at 1,600℃ have a maximum value of a 6.9 MPa·m1/2 and a 6.2 MPa·m1/2, respectively at the composition of containing 20 wt% Al2O3. It should be noticed that the mechanical properties and the sintering density of the Al₂O₃-3YSZ composites can be enhanced by using more fine Al₂O₃ powder due to their denser microstructure and smaller grain size.

In this study, some materials are organized and experimented with variables to obtain the optimum mix proportion for the mechanical property of halogen free flame resistance compound with varying addition of nano clay. Tensile strength, density and stiffness are tested in the room temperature. In this study, unlike existing layered structure, nano clay with tabular structure is used and sufficient stiffness, strength, thermal stability and gas block capability can be achieved with small amount of addition. Tensile strength and elongation test show high rupture strength only in specimens with compatibilizing agents while density test shows average measurement in all the specimens except T-9. It was confirmed that the measurement value according to the additives in compatibilizing agent or in nano clay of hardness test represents similarly.

In this paper, we present a novel hydrophilic coating material (Wellture Finetech, Korea) which can be utilized as a coating layer for anti-contamination for electrical and electronic system. The coating material was deposited on 4 inch silicon wafer with several different film thickness. The film thickness was controlled by spin coating speed. After curing of the film, we have scratched by permanent marker to check self-cleaning property of the film. Also we have executed several mechanical tests of the films. As the spin coating speed is increased, the film thickness was thickness was thinned from 230 nm to 125nm. Contact angle of the film lowered from 30° to 12° as the spin coating speed is increased from 700 to 2,500rpm. On permanent marker scratched film surface coated at 1,000 rpm. We have poured regular city water to investigate self cleaning property of the film. The scratches were gradually separated from the film surface due to super-hydrophilicity of the film. Hardness of coated film was 9H measured by ASTM D3363 method. And adhesion of all film was 5B tested by D3359 method. Also, to get exact hardness value of the film, we have utilized a nano-indenter. As spin speed is increased, the hardness of film was increased from 3 Gpa to 5 Gpa.